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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * The Universal Permissive License (UPL), Version 1.0
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 * person obtaining a copy of this software, associated documentation and/or
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 * (a) the Software, and
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 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
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 * is contributed by such licensors),
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
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 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
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package com.oracle.truffle.api.utilities;

/**
 * An utility value with three states, {@link #TRUE}, {@link #FALSE}, and {@link #UNDEFINED}.
 * {@link TriState} is preferable to using a {@link Boolean} value with {@link Boolean#TRUE},
 * {@link Boolean#FALSE} and <code>null</code>, because {@link Boolean} has a public constructor
 * which requires the use of {@link Boolean#equals(Object)} to compare the values. The comparison
 * with {@link Boolean#equals(Object)} is too slow.
 *
 * @since 20.2
 */
public enum TriState {

    /**
     * The state is true. Similar to {@link Boolean#TRUE}.
     *
     * @since 20.2
     */
    TRUE,

    /**
     * The state is false. Similar to {@link Boolean#FALSE}.
     *
     * @since 20.2
     */
    FALSE,

    /**
     * The state is undefined. Similar to <code>null</code>.
     *
     * @since 20.2
     */
    UNDEFINED;

    /**
     * Create a {@link TriState} from a primitive boolean.
     *
     * @since 20.2
     */
    public static TriState valueOf(boolean b) {
        return b ? TRUE : FALSE;
    }

    /**
     * Create a {@link TriState} from a boxed {@link Boolean} explicitely checking for
     * <code>null</code> and returning {@link #UNDEFINED}.
     *
     * @since 20.2
     */
    public static TriState valueOf(Boolean b) {
        return b == null ? UNDEFINED : (Boolean.TRUE.equals(b) ? TRUE : FALSE);
    }

}
